Answers

We first need to number on sites and dates with and without a partition. The difference betweens this numbering is constant as long as the level does not change. Then we can number once more, partitioning on this difference:

We first need to number on sites and dates with and without a partition. The difference betweens this numbering is constant as long as the level does not change. Then we can number once more, partitioning on this difference: